1. Field of the Invention
This invention relates to deformable mirrors for use in laser systems and more specifically to a multi-actuator deformable mirror that will cancel laser wavefront phase errors caused by the quasi-static aberrations occurring in large aperture metal mirror optics.
2. Description of the Prior Art
Large aperture high power laser resonator and beam transport optics, particularly metal mirrors and salt windows, produce quasi-static wavefront aberrations that reduce output beam quality and thus target irradiance. There exists physical and economic limitations on the primary optical quality obtainable in these elements as well as a high probability of subsequent reduction of quality due principally to material creep, and thermal or mounting distortions. Therefore, it is reasonable to consider the use of a quasi-static deformable mirror in the optical train as a wavefront error correction device to maximize target irradiance.
Other mirror systems such as those described in U.S. Pat. Nos. 4,060,314; 4,060,315; 3,967,899; and 3,904,274 describe mirror mounts, piezoelectrically-driven and ball screw-driven devices; however, nowhere is there described a multi-actuator deformable mirror with dither which comprises a copper-surfaced, aluminum faceplate supported by an aluminum back structure, actuated by nineteen differential ball bearing screws, and driven by stepping motors capable of 400 steps/rev when operating in "half step" mode.